1. Field of the Invention
The invention is directed to a seal arrangement for a vacuum valve with a valve body in which is arranged a valve opening having a longitudinal axis and which has an inner jacket surface surrounding the valve opening and forming a valve seat, and with a valve plate which closes the valve opening in the closed state of the vacuum valve and which has an outer jacket surface surrounding the valve plate, said inner jacket surface and said outer jacket surface being located opposite one another in the closed state of the valve.
2. Description of the Related Art
Seal arrangements for vacuum valves of the kind mentioned above usually have a seal which is arranged at the valve plate and contacts a sealing surface provided at the valve seat of the valve body when closed. Occasionally, the sealing ring is also arranged at the valve seat and the sealing surface is provided at the valve plate, for example, when a particular cooling device is to be provided for the sealing ring.
Besides seal arrangements in which the sealing ring is arranged at the broad side of the valve plate, arrangements of the sealing ring at the narrow-side outer jacket surface of the valve plate are also known. In this case, the sealing surface and the jacket surface of the valve body have a conical shape. Such arrangements of the sealing ring and sealing surface can be provided, for example, in corner valves and are especially common in butterfly valves, as they are called.
Vacuum valves in the form of butterfly valves are known in different embodiment forms. In these butterfly valves, the valve plate is initially swiveled relative to the valve seat in order to open the valve and is then rotated by about 90xc2x0 so that, when the valve opening is viewed from the end, only the narrow side of the valve plate is visible and the valve plate accordingly essentially releases the valve opening. Butterfly valves of this type are known in particular from U.S. Pat. No. 4,634,094 and German Patent DE 35 33 937 C1, whose contents are hereby adopted in the present application. A supporting shaft carrying a ball joint member which is supported in the housing so as to be swivelable on all sides is provided at the edge of the valve plate on one side and, in a diametrical arrangement, a connection part is provided on the other side. This connection part carries a pin which is guided in a link of an axially displaceable selector shaft or switching rod. The opening movement and closing movement of the valve plate is conveyed through an axial movement of the switching rod via this link. In the final phase of the closing movement shortly before the sealing ring is pressed against the sealing surface, the closing movement of the valve plate is approximately parallel to the valve opening.
Further, U.S. Pat. No. 3,722,852 discloses a seal arrangement in which a sealing ring, a sealing diaphragm and a supporting ring are provided at the valve plate. The sealing ring and the supporting ring are arranged in a depression surrounding the broad side of the valve plate in the area of its edge, and the supporting ring serves to limit the movement of the sealing plate relative to the valve seat in order to prevent jamming of the sealing diaphragm between the valve plate and a projection of the valve seat. The supporting ring is screwed to the valve plate and the sealing ring is connected to the supporting ring by a positive engagement.
The seal arrangement known from U.S. Pat. No. 4,208,035 has a one-piece seal element which is provided with a sealing ring arranged at the free end of a spring arm. A supporting portion of the sealing element is provided for limiting the deflection of the sealing ring through the valve plate in the closed state of the valve, this Supporting portion being ring-shaped as a whole. This metal seal element forming the valve seat is welded to the valve body.
One object of the invention is to provide a seal arrangement which can be used advantageously in a valve of the type mentioned above and in which the pressing of the sealing ring is limited in the closed state of the valve. A further object of the invention consists in providing a seal arrangement for a vacuum valve of the type mentioned in the beginning which can be assembled and, if required, also disassembled in a simple manner. It is a further object of the invention to provide a seal arrangement for a vacuum valve of the type mentioned in the beginning in which the pressing of the sealing ring is limited in the closed state of the valve and in which only comparatively few particles are released into the vacuum when closing and opening the valve and whose production costs are relatively low.
A seal arrangement, according to the invention, for a vacuum valve of the type mentioned in the beginning comprises:
a sealing ring which is arranged in an annular groove arranged at the outer or inner jacket surface and which has groove flanks and a groove base,
a sealing surface which is provided at the inner or outer jacket surface and which has a conical shape relative to the longitudinal axis of the valve opening and which is contacted by the sealing ring in the closed state of the vacuum valve,
wherein the distance of the groove base from the longitudinal axis of the valve opening changes along the width of the groove at least in the position occupied by the valve plate in the closed state of the vacuum valve and, further, a supporting ring is arranged in the groove laterally next to the sealing ring to limit the deformation of the sealing ring in the closed state of the vacuum valve, and when the groove is formed in the outer jacket surface of the valve plate this supporting ring is located on the side of the sealing ring on which the groove base has a greater distance from the longitudinal axis, and when the groove is formed in the inner jacket surface of the valve body this supporting ring is located on the side of the sealing ring on which the groove base has a smaller distance from the longitudinal axis,
and wherein a side surface of the supporting ring facing the sealing ring, together with the portion of the groove base located next to the supporting ring and the adjoining groove flank, define a receiving space for the sealing ring contacting this side surface of the supporting ring and increase the width of this receiving space toward the groove base.
Due to the fact that the groove base increases or decreases along the width of the groove, the supporting ring which is generally made from a material with little or no ductility or compressibility and/or from a material with little or no deformability can be inserted easily into the groove. The supporting ring requires little or no ductility or compressibility and/or little or no deformability while nevertheless contacting the base of the groove in the inserted state. The sealing ring can subsequently be inserted into the receiving space which is formed when the supporting ring is installed. Because of the increase in width in the receiving space toward the base of the groove, it is possible to snap the sealing ring into this receiving space and/or a free space remains in the installed state of the sealing ring and the material of the sealing ring can be pressed into this free space when the sealing ring is pressed against the sealing surface.
The various features and developments according to the invention are given in the claims.